Plasma processing is employed in fabrication of integrated circuits, masks for use in photolithographic processing of integrated circuits, plasma displays and solar technology, for example. In the fabrication of integrated circuits, a semiconductor wafer is processed in a plasma chamber. The process may be a reactive ion etch (RIE) process, a plasma enhanced chemical vapor deposition (PECVD) process or a plasma enhanced physical vapor deposition (PEPVD) process, for example. Recent technological advances in integrated circuits have reduced feature sizes to less than 32 nanometers. Further reductions will require more precise control over process parameters at the wafer surface, including plasma ion energy spectrum, plasma ion energy radial distribution (uniformity), plasma ion density and plasma ion density radial distribution (uniformity). In addition, better consistency in such parameters between reactors of identical design is required. Ion density is important in PEPVD processes, for example, because ion density at the wafer surface determines deposition rate and the competing etch rate. At the target surface, target consumption (sputtering) rate is affected by ion density at the target surface and ion energy at the target surface.
Currently, uniformity of PEPVD deposition rate and deposited film properties cannot be precisely controlled, and is dependent upon chamber geometry, such as a large wafer-to-target distance. There is a need to precisely adjust or control uniformity of deposition rate, by controlling ion density distribution across the wafer surface. There is a need to precisely adjust or control uniformity of deposited film properties by controlling ion energy distribution across the wafer surface.